Stepping into a gym for the first time can feel like submerging yourself in a world of strange equipment that doesn't make much sense. The easiest place to start is with cardio machines. Most of them use intuitive motions that you may already be familiar with such as walking, running, pedaling a bike or climbing stairs. Once you're ready to venture out of the cardio area, familiarize yourself with one or two pieces of equipment at a time so you don't feel overwhelmed.
The power rack allows you to lift heavy weights without a spotter. Its steel rails outline a cube or hollow rectangle you can step into. The barbell goes straight through the middle of the cube, protruding out the middle of the sides. You can set safety stops at any level you want. If you're doing a bench press, for example, you'd set the stops at just above chest height so that if you work out to failure, the bar will come to rest on the stops.
The Smith machine is a barbell housed in a fixed vertical or near-vertical track. It performs much the same purpose as a standard weight-training machine, limiting the barbell to a set range of motion. Like the power rack, you can set safety stops to keep the bar from falling below any given height. There's a hook on each end of the Smith bar, which can latch onto a racking peg at any point along the rail. So the Smith machine is, essentially, self-spotting.
BOSU balls resemble half an exercise ball mounted on a rigid plastic platform. Sitting, standing or lying on either side of the ball forces your muscles to compensate for the ball's added instability.
There are wrist roller machines, but it's more common to see a "free weight" wrist roller, a short bar with a length of rope attached to it and a weight plate at the end of the rope. To work your wrist extensors with the wrist roller, hold the short bar with your palms facing down then rotate the bar toward you, spooling the rope around it to lift the weight.
Cable machines link interchangeable handles to a weight stack, by means of a cable that runs through a pulley. The pulley may be fixed or adjustable. Usually adjustable pulleys slide along a rail, but functional trainers have pulleys mounted on swing arms that adjust through several planes. Cable machines may have one or more pulleys. The numerous positions you can manipulate the pulleys into, and the various handles you can use, allow you to perform conventional weight training exercises or simulate sports movements, such as a tennis serve.
Plyometric or "plyo" platforms are sturdy boxes or elevated platforms of varying height. You perform jumping exercises with these platforms to build power. You can also use them as elevated bases for strength-training exercises such as leg dips or step-ups.